Portable power tools are often utilized in areas, such as in enclosed indoor facilities or outdoors in residential neighborhoods, where the noise generated by the power tool may create a health risk and/or a public nuisance. The noise emanating in horizontal directions from portable power tools is especially critical because this noise tends to directly impact upon the people located in the vicinity of the power tool. In recognition of this phenomenon, standards and local ordinances restricting the maximum acceptable noise level from portable power tools are becoming increasingly common. One example of a standard is ANSI B175.2-1996 issued by the American National Standard Institute.
Power blowers are one example of a portable power tool where noise is of special concern. In addition to the noise generated by the engine, power blowers also produce noise from the blower fan and the associated air flow. Noise is especially problematic for power blowers utilizing a backpack mounted engine and fan unit because, typically, such blowers utilize a relatively large engine and have a relatively large air flow.
While some conventional portable power tools, including backpack mounted power blowers, are capable of meeting at least some of the current standards and ordinances, there is a continuing desire to reduce the noise associated with such tools.